1. Field of the Invention
The invention relates to a brake device in which a disc rotor is arranged between a hub and a wheel.
2. Description of Related Art
A brake device generates braking torque by forcing a pad into contact with a rotating disc rotor by hydraulic pressure from a hydraulic cylinder, for example. In this brake device, when the pad contacts the rotating disc rotor, vibration occurs, and so-called brake noise is produced by the rotating disc rotor and the pad resonating. Here, brake noise includes both out-of-plane noise and in-plane noise. Out-of-plane noise is caused by out-of-plane vibration (i.e., vibration in the out-of-plane direction) in which a friction surface of the disc rotor that the pad contacts vibrates in the same direction as a rotation axis. In-plane noise is caused by in-plane vibration (i.e., vibration in the in-plane direction) in which the friction surface of the disc rotor vibrates in the circumferential direction of the disc rotor.
For in-plane vibration, Japanese Patent Application Publication No. 2004-019715 (JP 2004-019715 A) proposes a method that involves estimating an eigenvalue of in-plane vibration of the disc rotor (hereinafter, this value will simply be referred to as an “in-plane eigenvalue”). Using estimating technology such as that described in JP 2004-019715 A, it is possible to set the in-plane eigenvalue of the disc rotor to a desired value.
The disc rotor is assembled between a hub and a wheel, and is connected to the hub and the wheel. Therefore, the in-plane eigenvalue of the disc rotor when the disc rotor is fastened to the hub and the wheel may change, depending on the method by which the disc rotor is fastened to the hub and the wheel. If the in-plane eigenvalue of the disc rotor when the disc rotor is fastened changes, in-plane noise may not be able to be effectively suppressed by assembling the disc rotor to the hub and the wheel, even if the disc rotor is designed to suppress in-plane noise.